1. Field of the invention
The present invention relates, in general, to a mass measurement system in a gravity-free environment and, more particularly, to a mass measurement system and method using inertial force and standard mass in a gravity-free environment, which apply the same linear acceleration both to a sample, which is a measurement object, and a standard sample having a known mass, and utilize only the inertial forces of the sample and standard sample, caused by the applied linear acceleration, and the mass of the standard sample, thus efficiently measuring the mass of the sample.
2. Description of the Related Art
Generally, the inside of a spacecraft traveling in space is in a micro gravity environment having little gravity, or in a gravity-free environment. In order to measure the mass of medicine, material, animal, plant, etc., in such a micro gravity or gravity-free environment, the following methods using a mass measurement device, which is known as a so-called “space mass measuring device”, have been proposed.
First, there is a method of connecting a spring or metallic bar to a sample, applying a vibration to the sample, measuring the period of the vibration, and calculating the mass of the sample using a spring mass and metallic mass system. Second, there is a method of linearly accelerating a sample using a constant force, measuring an acceleration and calculating mass. Third, there is a method of rotating a sample and measuring the mass of the sample using the measurement of a centrifugal force.
However, the above-described conventional methods of measuring the mass of a sample, etc., in a gravity-free environment accompany the following problems.
First, the mass calculation method using the spring mass and metallic mass system is problematic in that it is difficult to precisely measure a period due to the damping effect of the system itself, and repetitive measurements must be performed for a long period of time to precisely measure a precise period.
Further, a vibration system itself is a non-linear system, so that it is very difficult to obtain mass from a vibration period, and measurements are subject to error. Therefore, the spring mass and metallic bar mass system currently used in a spacecraft is problematic in that an error of about 1% is caused at the time of measurement, so that it is difficult to perform precise measurement.
Therefore, such a spring mass and bar mass system has been limitedly used for the rough measurement of the mass of an astronaut which does not particularly require precise measurement.
Next, the method of applying a constant force to linearly accelerate a sample, measuring acceleration and obtaining the mass of the sample is problematic in that it is difficult to accurately provide a constant force, and, in addition, it is very difficult to precisely measure acceleration. Therefore, the method of applying a constant force to linearly accelerate a sample, measuring acceleration and obtaining mass is problematic in that there is considerable error due to the imprecision of measurement.
Therefore, the method of applying a constant force to linearly accelerate a sample, measuring acceleration and obtaining mass is also used for the measurement of the rough mass of an astronaut which does not particularly require precise measurement.
Next, the method of rotating a sample and measuring the mass of the sample using the measurement of a centrifugal force is problematic in that the diameter of a system must be large to apply a sufficient centrifugal force, and a signal must be extracted from a rotating shaft, thus complicating a system. Further, there is a problem in that, when an animal, which is a main mass measurement object, is rotated, stress is applied to the animal.
Further, the above-described conventional methods are technologies for approximately measuring mass, and are not suitable for the precise measurement (with an error of 1% or less) of small mass (for example, a mass of 5 kg or less) for space experiments, the importance of which has been recently emphasized.
Further, due to the problems and limitations of the conventional methods, precise measurements prior or subsequent to an experiment on a sample are mainly performed on earth, so that a large inconvenience is caused, thus the precision and efficiency of space experiments are greatly limited.